1. Field of the Invention
The present invention relates to a technique of constructing a multipath of a storage system in consideration of redundancy for hot-swap of firmware in a storage device.
2. Description of the Related Art
A storage system is composed of a host and a storage device connected to the host. Upon hot-swap of firmware in such a storage device, if plural control modules (hereinafter referred to as “CMs”) having firmware components installed thereto are provided, the firmware components are exchanged in two stages, the first half and the second half. For example, if the storage device includes four CMs, firmware components of two CMs are first exchanged at the same time. After the completion of the exchange, firmware components of the remaining two CMs are exchanged. The storage device and the host constitute multipath construction. Each path is connected to each CM to thereby enable hot-swap of firmware without stopping an operation. Next, an example of hot-swap of firmware in a device including two CMs is described.
FIGS. 1A to 1D are explanatory views of firmware exchange of the related art. A storage system is composed of a host 101 and a storage device 102 having two paths connected to the host 101. (FIG. 1A) In a general state, data can be transferred to the storage device 102 from the host 101 through the two paths. (FIG. 1B) During exchange of firmware of the first half (CM 0), data is transferred between the host 101 and the storage device 102 only through the path on the CM 1 side. (FIG. 1C) During exchange of firmware of the second half (CM 1), data is transferred between the host 101 and the storage device 102 through the path on the CM 0 side where firmware exchange is completed. (FIG. 1D) After the completion of exchange of firmware of the second half, data can be transferred through the two paths.
As described above, the storage device 102 and the host 101 constitute multipath construction. Each path is connected to each CM to thereby enable hot-swap of firmware components without stopping an operation.
However, if firmware exchange is carried out under the following circumstances, connectivity of all paths between the storage device and the host is abnormal. As a result, data transfer is disabled and an operation is stopped.
(1) All cables connected between the storage device and the host are connected to the first half, the CM 0.
(2) All cables connected between the storage device and the host are connected to the second half, the CM 1.
In the environment where multipath information has been already generated, if active firmware exchange is carried out under this condition, an operation is stopped. However, the host needs to be reactivated in order to change path construction. As a result, the operation is further suspended. Therefore, in this case, this firmware exchange is the same as inactive firmware exchange.